This invention relates to a tripod type constant-velocity joint in which torque is transmitted between an outer ring, formed with three track grooves in its inner periphery, and a tripod member mounted in the outer ring.
Tripod type constant-velocity joints are known in which three axially extending track grooves are formed in an inner periphery of an outer ring, roller guide surfaces formed in respect track grooves so as to oppose one another in a circumferential direction are cylindrically shaped, a tripod member mounted in the outer ring has trunnions at positions corresponding to respective track grooves, and spherical, rollers pivotably supported by the trunnions are arranged in the track grooves so as to transmit torque between the outer ring and the tripod member at portions where the spherical rollers engage roller guide surfaces of the track grooves.
With such a tripod type constant-velocity joint, when torque is transmitted with the outer ring and the tripod member taking a working angle, centers of rotation of the spherical rollers are inclined relative to length directions of the track grooves. Due to this inclination, the spherical rollers will not make a pure rolling motion, and relative slip occurs between the spherical rollers and the roller guide surfaces on the track grooves.
Therefore, frictional resistance increases at contact portions between the spherical rollers and the roller guide surfaces, so that slide resistance is large when the outer ring and the tripod member relatively move in an axial direction. Thus, pivoting and noise are produced and NVH (noise, vibration and harshness) properties lower.
In order to improve the NVH properties, in a tripod type constant-velocity joint described in JP patent publication 64-5164, raceway grooves extending in an axial direction are formed in side faces of track grooves formed in an outer ring, raceway grooves are formed on both sides of guide blocks supported by trunnions of a tripod member so as to be pivotable in a moving direction of the tripod member relative to the trunnions, and a plurality of balls are mounted between the guide blocks and the outer ring so as to transmit torque between the outer ring and the tripod member through the balls.
In this tripod type constant-velocity joint, even when the outer ring and the tripod member take a working angle, the guide blocks are maintained at a constant position by the balls mounted between the raceway grooves on the guide blocks and the raceway grooves on the outer ring. Thus, this tripod type constant-velocity joint is characterized in that when the outer ring and the tripod member relatively move in the axial direction, the balls move while rolling, so that vibration and noise are less likely to be produced and the tripod type constant-velocity joint exhibits good NVH properties.
In the tripod type constant-velocity shown in this publication, it is necessary to provide a ball dropout preventive portion for preventing the balls from dropping out at both ends of the raceway grooves on the guide blocks. Thus, when a working angle between the outer ring and the tripod member increases, the balls will contact the dropout preventive portion, so that they cannot smoothly roll, thus producing slip. This worsens the NVH properties in a slip region.
In order to solve such a problem, as shown in FIG. 6, a tripod type constant-velocity joint is proposed in which a plurality of balls 35 are mounted between raceway grooves 31 formed on both sides of each track groove 30 and raceway grooves 34 on both sides of a guide block 33 pivotably supported by each trunnion 33 of a tripod member to maintain a position of the guide block 33. The balls 35 are retained by a retainer 36, and a moving distance of the retainer 36 is restricted to half of a moving distance of the guide block 33 by virtue of a moving distance restricting device to cause the balls 35 to always make a rolling motion.
In the tripod type constant-velocity joint shown in FIG. 6, when an outer ring and tripod member transmit torque while taking a maximum working angle, the balls 35 located at both ends of the retainer 36 can come off the raceway grooves 34 of each guide block 33. Thus, the retainer 36 has to be of such a structure as to prevent the balls 35 from dropping out of the raceway grooves.
Thus, with the retainer 36 in the tripod type constant-velocity joint shown in FIG. 6, the balls 35 are held by two pressed plate members 36a, 36b having a plurality of semispherical pockets 37, and the plate members 36a and 36b are coupled together by caulking a plurality of rivets 38.
In the tripod type constant-velocity joint shown in FIG. 6, since the balls 35 can always roll normally, NVH properties are superior. But, the retainer 36 is of such a structure that a number of parts is large because the two pressed plate members 36a, 36b are coupled together by caulking a plurality of rivets 38. Further, it is necessary to join the plate members 36a and 36b together so that the pockets 37 formed in the plate members 36a and 36b align with one another. Thus, it is extremely troublesome to assemble the retainer 36 and its cost is high. Thus, improvement is desired in achieving reduced cost and a lighter weight for a tripod type constant-velocity joint.
An object of this invention is to provide an improved tripod type constant-velocity joint which is superior with regard to NVH properties, low in cost and light in weight.
According to this invention, there is provided a tripod type constant-velocity joint comprising an outer ring, and a tripod member mounted in the outer ring. The outer ring is formed with three axially extending track grooves in an inner periphery thereof, and straight raceway grooves are formed in respective side faces of each track groove so as to extend in an axial direction of the outer ring and circumferentially oppose each other. The tripod member has three trunnions at positions corresponding to the track grooves, and guide blocks are supported by respective trunnions in the track grooves so as to be pivotable relative to the trunnions in a moving direction of the tripod member. The guide blocks each have raceway grooves on respective sides thereof so as to oppose the raceway grooves formed in a corresponding track groove. A plurality of rolling elements are mounted between the opposed raceway grooves, and retainers retain the rolling elements. A moving distance restricting unit restricts a moving distance of the retainers relative to half of a moving distance of the guide blocks. This tripod type constant-velocity joint is characterized in that the retainers comprise plate members each made of metal and having a plurality of pockets to receive the rolling elements, and a plurality of claws are provided on a periphery of each pocket and project in opposite directions, whereby the rolling elements are mounted in the pockets while elastically deforming the claws.
Since the retainers have a structure such that a plurality of pockets for receiving the rolling elements are formed in plate members, and a plurality of jaws are provided on a periphery of each pocket so as to extend in opposite directions, easy-to-manufacture, light-weight retainers are provided, so that it is possible to achieve reduced cost and lessened weight.
Since the rolling elements are mounted in the pockets while elastically deforming the claws, the rolling elements are prevented by the claws from coming out of the pockets, so that it is possible to reliably retain the rolling elements in the pockets. By providing two claws on a periphery of each pocket at opposed positions so as to extend in opposite directions, it is possible to prevent the rolling elements from coming out of the pockets.
Further, by providing four claws on a periphery of each pocket at 90xc2x0 intervals so that a first set of two claws and a second set of two claws extend in opposite directions, it is possible to reliably prevent rolling elements from coming out of the pockets.
In the tripod type constant-velocity joint according to this invention, by forming the retainers by performing a pressing operation, it is possible to achieve further reduction in terms of cost of the constant-velocity joint.